Pick-up device



March 10, 1931- J. H. BUTCHER ET AL 1,796,238

PICK-UP DEVICE Filed May 1, 192

Invenfors Jchn H. Bufcher, FY six pwms,

Their" Afiorne g.

Patented Mar. 10, 1931 UNITED STATES ATE T OFFICE" JOHN H. BUTCHER, OFRUGBY, AND FELIX P. WILLS, OF UXBRIDGE, ENGLAND, ASSIGN- ORS TO GENERALELECTRIC COMFANY, A CORPORATION OF N EW YORK PICK-UP nnvrcn Applicationfiled May 1, 1925, Serial No. 105,970, and in Great Britain May 26,1925.

Our invention relates to apparatus by means of which the movements of arapidly oscillating member are converted into corresponding electricaloscillations. More particularly our invention relates to a soundreproducing apparatus, such for example as a phonograph, wherein thevibrations of a member engaging a sound record are converted intoelectric oscillations which by to other means may be amplified andconverted into sound waves and an object of our invention is theprovision of an improved apparatus of this character.

Our invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and

its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a cross acsectional view of oneembodiment of our invention and Figs. 2 and 3 are similar views showingmodifications thereof.

Inasmuch as apparatus of the type to which our invention relates are nowcom- 25 monly known as pick-up devices, this term will, for convenience,be used throughout the description and claims in referring to thisapparatus.

In the drawing we have shown a main supporting member l in the form of aring which is adapted to be applied to the end of the tone arm of aphonograph in place of the usual diaphragm supporting head. In thisconnection we use the term phonograph as applying to any soundreproducing or talking machine having a stylus which is vibrated bycontact with a sound record. A permanent ma net 2, which in Fig. 1, isin the form of a fl at annulus is supported from the ring 1 by thesleeve 3 which preferably is of magnetic material and forms a pole piecefor the magnet. Secured to the outer periphery of the magnet is themagnetic member 4 having the central core or pole piece portion 5 whichwith the sleeve 3 forms an annular air gap in the magnetic circuit. Inthis air gap is the spool 6 which is of light construction and whichcarries the coil 7. The spool with the coil thereon is supportedcentrally in the air gap and isoperatively connected bythe rod 8 and arm8 to the stylus holder 9 having the stylus 10 whereby vibrations of thestylus cause corresponding vibrations of the coil 7 in the axialdirection. For centralizing the coil in the air gap we provide themember 11 which preferably is in the form of a mica diaphragm havingholes therein to make it noiseless. However, this member may, ifdesired, be in the form of a spider or may be a diaphragm of othermaterial than mica. The member 11 is shown flexibly supported betweenthe rings 12. Thedisk 13 of insulating material is secured to thesleeve3 and carries the binding posts 14: connected respectively to the twoends of coil 7.

In the modification shown in Fig. 2 the arrangement of parts issubstantially the samev as in Fig. 1 except that the permanent magnet 17has an outer flange portion which engages the magnetic member 18 ofcorresponding modified form.

In the modification shown in Fig. 3 the magnet is flat as in Fig. 1, atubular magnetic member 20 supports the stylus holder 9 from I theperiphery of the magnet and a second magnetic member 21 connects withthe inner portion of the magnet and, in cooperation with the member 20,forms the air gap in which moves the coil 22 carried by the spool;

23. The spool 23 in this case connects directly with the arm 8 andcentralizing member 11. The member 21 is secured directly to thesupporting member 24. corresponding to member 1 of Figs. 1 and 2.

In the use of this apparatus, the usual head carrying the sounddiaphragm is removed from the tone arm of the phonograph and the support1 or 24 is applied thereto with the stylus resting on the moving recordin the usual manner. The resulting vibrations of the coil cause electricimpulses to be induced therein. These impulses may be amplified bysuitable electron discharge amplifying devices and then converteddirectly into sound. as for example by a telephone or a loud speaker, orif desired they may be utilized to modulate radio transmission waves.

What we claim as new and desire to secure by Letters Patent of theUnited States, is,

'1. In combination, magnetic poles arranged to form'an' air gap, a coilmountedin the air gap coil support means extending through oneof saidpoles and means adapted to be vibrated by engagement with a sound.recordfor bodily moving said support and said coil in an axialdirection.

2. A p ck-up device comprisingina-gn'etic poles arranged to form an airgap-thereima coil mounted insaid.air -gap, coilsupport means extendingthrough one of said poles and arr'anged'to move said coil'axially astylus, and means connecting the stylus with said support means.

3. Api'ck-up device comprisinga support, a magnetic member'compris'iiiga magnet having-an annular airgz'ap, a coil, means com, prising anoiseless diaphragm foncentralizing' the coilin theair gap, astyius, andmeans connecting the stylus with the coil through said diaphragm wherebyvibrations of thestyluscaiise the coil to vibrate axially.

4. A phonographic pick-up device comprising asupport adapted tobe'attached to the tone arm vof a phonograph, a permanent magnet, amagnetic member associated with the magnet and forming therewith anannu- '.lar'air gap a"generative-coil, means compiis nga noiseless diphragmfor supporting the coilin'theair gap for axial inovementtherein, astylus adapted 'to follow a a phonograph recoi'd,'*anda connectioncomprising a pivotal support between the'stylus andithe'coil. 1

v In'witnes's whereof, ,we have hereuntos't our hands thisj13th dayofApril, 1926. JOHN BUTCHER.

FELIX P. WILLS.

